Evaluative metering

[Yisehaq]

Hey photo experts,

I am working on my exposure skills for sometime now. I am now okay with partial and center weighted but evaluative is a big problem to me.
For evaluative from what I know you don't have to compensate like 18% gray issue. What I read in other site is that you might need to compensate may be -2/3 in order not to blow out the bright parts. So I always put the indicator at 0 no matter the tonality, brightness etc. Is that right?
But almost all ways if there is a variation in lighting from shadow to bright there is always unsatisifactory result. But ofcourse the pictures are always acceptable but need more work on post processing.

Any advice.

[Ben H]

So I always put the indicator at 0 no matter the tonality, brightness etc. Is that right?

No.

One of the problems new photographers come across when learning, is that they think the camera knows better than them.

Metering in a camera is a "tool" to help you better achieve what you want. it is not an end unto itself. The reason that tools like exposure compensation exist are to quickly let *you* tell the camera what you want the picture to be like, not to force you to set the camera to what *it* thinks is *correct* (because in general, there is no such thing as *correct* in art).

When you choose evaluative metering, you are simply saying to the camera "give me your exposure metering in a particular way" - in the case of evaluative, the camera does a number of things to meter the scene. I won't go into exactly what it does here.

But the bottom line, just because the camera meters a particular scene in a particular mode and you set the controls to give you a "correct" exposure based on that metering decision *doesn't* mean that automatically gives you the best picture. The buck stops with you, not your camera!

It's a learning curve, but over time, and with some effort, you get used to what the camera will meter in any given mode for any given scene, and what you have to do to get the results that work for you.

But don't be afraid to underexpose or overexpose a picture (based on what the camera is metering) - ithis does not mean the picture is wrong. In many cases, using exposure compensation *is absolutely necessary* to get the pictures that you want.

Remember, the metering is a guide to help you make decisions. Leaving the camera to make these decisions for you (eg leaving it in auto modes and letting the camera decide) not only will *not* give you great pictures in most cases, it also means you aren't the photographer, and you're not learning and understanding what you are doing.

Don't let the camera dictate to you - remember, *you're* the boss!

I hope that helps!

[Marko]

EXCELLENT EXCELLENT POST BEN H :highfive: :highfive:

You are of course 100% correct. Cameras do not have brains. They spit out an exposure reading (usually accurate in NORMAL light with a variety of tones) but they have no idea what they are looking at. (The camera can't tell if it's looking at a rock or a dog) This unfortunately means that the camera will make many mistakes. You the photographer have to know when to VETO the camera's exposure reading. Comes with experience and practice.


No.

One of the problems new photographers come across when learning, is that they think the camera knows better than them.

Metering in a camera is a "tool" to help you better achieve what you want. it is not an end unto itself. The reason that tools like exposure compensation exist are to quickly let *you* tell the camera what you want the picture to be like, not to force you to set the camera to what *it* thinks is *correct* (because in general, there is no such thing as *correct* in art).

When you choose evaluative metering, you are simply saying to the camera "give me your exposure metering in a particular way" - in the case of evaluative, the camera does a number of things to meter the scene. I won't go into exactly what it does here.

But the bottom line, just because the camera meters a particular scene in a particular mode and you set the controls to give you a "correct" exposure based on that metering decision *doesn't* mean that automatically gives you the best picture. The buck stops with you, not your camera!

It's a learning curve, but over time, and with some effort, you get used to what the camera will meter in any given mode for any given scene, and what you have to do to get the results that work for you.

But don't be afraid to underexpose or overexpose a picture (based on what the camera is metering) - ithis does not mean the picture is wrong. In many cases, using exposure compensation *is absolutely necessary* to get the pictures that you want.

Remember, the metering is a guide to help you make decisions. Leaving the camera to make these decisions for you (eg leaving it in auto modes and letting the camera decide) not only will *not* give you great pictures in most cases, it also means you aren't the photographer, and you're not learning and understanding what you are doing.

Don't let the camera dictate to you - remember, *you're* the boss!

I hope that helps!

[Ben H]

EXCELLENT EXCELLENT POST BEN H :highfive: :highfive:


Thanks - I'm glad I was able to get the point across. I'm still going through this learning curve myself (learning how the camera typically responds to various types of scenes and how to react accordingly) and there aren't really any shortcuts - you just have to feel your way and learn by experience.

But I do see this type of question a lot on many forums - it's like "photography-by-the-numbers". Personally, I'm a super-chimper while I'm learning - I know enough to get in the ballpark, but I go by what I want the picture to look like. Actually, I find quite a lot that I drop the exposure compensation down, as my camera (Canon 450D) has a tendency to produce pics a bit too bright for my tastes (scene depending of course). And if you're doing something like sunsets or anything tricky, the camera just isn't going to read your mind, so I do a lot of exposure compensation (and sometimes bracketing), or go to manual mode.

It might be an idea to tackle a podcast on this, perhaps? This misconception that the camera knows best, and can produce the pictures you want by reading your mind..?

[kat]

YES!! A podcast would be nice.

I am soo confused on this. I've been reading nonstop for the last couple of days and now I'm more confused than ever. I don't understand exposure with the camera!!!

I know when to use my S or A mode (haven't gotten to my M) - I'll set up what I think the value would be. If I don't like the image I produce I'll change it up either by the f-stop, shutter speed or EV value (ISO too). Is that how you change the exposure or am I missing something here? I know someone mentioned a spot meter but I don't understand..do I take a picture with what that spot meter read then do my changes or is it there a number I just don't see!!!

I've gone through my manual and Digital Field Guide but I'm missing something in my head..

[Ben H]

I know when to use my S or A mode (haven't gotten to my M) - I'll set up what I think the value would be. If I don't like the image I produce I'll change it up either by the f-stop, shutter speed or EV value (ISO too). Is that how you change the exposure or am I missing something here?

Generally speaking, if shooting in A (Aperture priority mode) you are saying to the camera "I want to use a particular f-stop", and the camera will adjust the other settings (shutter speed, sometimes ISO) in order to get the exposure "correct". Now, let's say we take this shot, but decide it's too bright. We can't alter the shutter speed (because the camera has chosen one for us in this mode, it's what we asked it to do), and while we could change the ISO setting (or the f-stop if we we're happy to change the depth of field), or move to manual mode and plugin all the previous settings and then adjust them accordingly (slow, and a bit of a pain), the easiest tool to use is the exposure compensation feature - this basically gives you up to a couple of stops under and over, to quickly let you adjust the overall expsoure (the camera will change the other settings accordingly).

In effect we are saying - "I'll take the settings you're giving me, but just pull the overall exposure up or down a bit for me". Hence, we are compensating for what the camera thinks is the correct exposure with what *we* want.


I know someone mentioned a spot meter but I don't understand..do I take a picture with what that spot meter read then do my changes or is it there a number I just don't see!!!

Most cameras have different metering modes. Let's take a simplified, hypothetical example to illustrate:- let's say we have a piece of card, the left half is bright white, and the right half is dark black, and we go to take a picture of it. In spot metering mode, the camera will meter based on the area you focus on, a really small area. if you focused on the white half, the camera would go "whoa, this is bright, better make the overall exposure darker". If you focused on the black half, the camera would go "whoa, this is really dark, let's crank up the exposure brighter".

Result - two different "correct" exposure readings on the same scene. Can you guess what each half of the card would look like in each case?

Now let's switch out camera to Evaluative metering. Now, this mode takes into account what you focused on, but also takes into account what's going on elsewhere in the scene. If we focused on the white half, the camera would go "Ok, our focusing bit is pretty bright, but over there in the black half it's quite dark. In fact, seems like half the scene is bright, and half is dark - better set a medium exposure to pull down the whites and pull up the darks".

You can see how different metering modes, and the scene we are shooting, can result in completely different "correct" exposures.

I generally recommend sticking to evaluative while learning - it's actually quite a complex mode that does a lot of complex things, takes readings from different parts of the frame, works out averages and other stuff too (most modern cameras actually have data from thousands of different types of scene that the camera compares the current scene to, to work out how best to set the exposure).

But there are situations when setting different metering modes can be useful. Centre-weighted average mode, for example, can be good when shooting backlit subjects - this ignores the over exposed background, and concentrates on getting your darker subject exposed correctly. It's like spot metering, but with a larger "spot".

Does that help illustrate what's going on, Kat?

[kat]

Yes..absolute sense! What I was thinking all along until I got into these equation stuff..lol.

So if I want the same "exposure" for the next shot..but put the camera in a different position..is that where the autoexposure lock button comes in?

[Ben H]

Yes..absolute sense! What I was thinking all along until I got into these equation stuff..lol.

Cool. Yep, don't let the numbers fool ya! :)


So if I want the same "exposure" for the next shot..but put the camera in a different position..is that where the autoexposure lock button comes in?

Yep. Or, you can use the settings you've just arrived at, and set them up in manual mode - now the exposure won't change at all (because in manual mode, we are no longer asking the camera to give us ballpark metering - we're saying "Don't bother telling me what they are, I can work out my own darn settings, thanks!")

*Thinks*: Actually, it would be nice to have a camera preference in which when you switch to Manual, the camera would automatically copy the settings of the last metered scene - in effect, a quick way to copy the settings from another mode to Manual, for increased control.

Mr Canon, are you listening..? :)

[kat]

Ha ha!

THANK YOU soo much! It can get quite overwhelming sometimes!!

:)

[Ben H]

You're welcome Kat - it's what we're here for :)

[djKianoosh]

Is "evaluative" metering the same as what Nikon calls "matrix"? just wanted to make sure the terminology is clear. where does the term "evaluative" come from? canon-speak?

[Ben H]

I think so, yes. See here for more detailed info:
http://www.kenrockwell.com/nikon/matrix.htm

"Evaluative" because the camera uses a bunch of different algorithms to evaluate how the scene should be exposed.

[Yisehaq]

thanks guys that is very helpful. I have one question though when I see on many forum I read that "Evaluative metering gets the correct exposure 90% of the time." True or Flase?

[Ben H]

Well it depends on what you are shooting, of course! ;)

But evaluative metering is a good general mode and is recommended for general shooting. My camera manual explicitly states this:

"Normally, evaluative metering is recommended."

[Marko]

thanks guys that is very helpful. I have one question though when I see on many forum I read that "Evaluative metering gets the correct exposure 90% of the time." True or Flase?

I'm not convinced it's 90% but it might be 80%

Here is the classic example to illustrate the point:

As far as Know If you fill the frame with 100% white (paper, sheet, towel whatever) there is NO metering mode that will give you a white result. It will ALWAYS be grey.

Why? Because the camera has no brain. It is set to average out the tones in any scene, so it makes the white sheet grey. And it is for this reason that you cannot depend on your camera's reading all the time. Only you, the human know what you are looking at.

[Yisehaq]

Understanding Exposure by Bryan Peterson is a very good book concerning exposure. I think its a must read. I learned a lot from it.

My a suggest a postcast of his interview if Marko knows the guy?;)

[dmagick]

Understanding Exposure by Bryan Peterson is a very good book concerning exposure. I think its a must read. I learned a lot from it.

My a suggest a postcast of his interview if Marko knows the guy?;)

I was going to suggest the same book :) I keep referring back to it every now and then.